1. Field of the Invention
The subject invention generally pertains to what is known as a sliding door and more specifically to a resilient door panel for such a door.
2. Description of Related Art
So-called horizontally sliding doors (which actually may slide or roll) usually include one or more door panels that are suspended by carriages that travel along an overhead track. The carriages allow the door panels to slide or roll in a generally horizontal direction in front of a doorway to open and close the door. The movement of the panels can be powered or manually operated. Depending on the width of the doorway and the space along either side of it, a sliding door can assume a variety of configurations.
For a relatively narrow doorway with adequate space alongside to receive an opening door panel, a single panel is enough to cover the doorway. Wider doorways with limited side space may require a bi-parting sliding door that includes at least two panels, each moving in opposite directions from either side of the doorway and meeting at the center of the doorway to close the door. For even wider doorways or those with even less side space, multi-panel sliding doors can be used. Multi-panel doors have at least two parallel door panels that overlay each other at one side of the doorway when the door is open. To close the door, one panel slides out from behind the other as both panels move in front of the doorway to cover a span of about twice the width of a single panel. Applying such an arrangement to both sides of the doorway provides a bi-parting door with multiple panels on each side.
Although sliding doors are used in a wide variety of applications, they are often used to provide access to cold-storage lockers, which are rooms that provide large-scale refrigerated storage for the food industry. Doorways into such a room are often rather wide to allow forklift trucks to quickly move large quantities of products in and out of the room. When closing off a refrigerated room, sliding doors are often preferred over roll-up doors and bi-fold doors, because sliding panels can be made relatively thick with insulation to reduce the cooling load on the room.
In providing an appropriate door panel for a cold-storage application, it can be desirable to have a relatively thick, rigid door panel. The thickness generally provides better thermal insulation; while the rigidity allows a panel to seal against gaskets mounted to the stationary structure surrounding the door. Alternatively, the panel itself may carry compressive seals, and the rigidity allows the panel to accurately position its seals and allows the door panel to transmit (in a direction generally coplanar with the panel) the necessary compressive forces required to tightly engage the seals. Unfortunately, a relatively thick, rigid door creates several problems, especially in cold-storage applications.
First, door panels for cold-storage rooms are usually power-actuated to minimize the amount of cool air that can escape from the room when the door is open. Thus, for rapid operation, it is desirable to have a door panel that is as light as possible to minimize its inertia. However, the mass of a relatively thick, rigid door tends to slow it down.
Second, for doors that are designed to open automatically in the presence of an approaching vehicle, such as a forklift, a slow opening door is susceptible to being struck by a fast moving vehicle. Moreover, a closed door limits a driver""s visibility to only what is in front of the door. Thus the opening of the door should be as quick as possible, not only for maintaining the temperature of the room, but also to avoid a collision between an approaching vehicle and an obstacle that may be just on the other side of the door.
Third, adding rigidity to a door panel can make it less tolerant of a collision. A stiff, rigid door panel may be more likely to permanently deform or break than a more flexible, resilient one. If a door panel is strong as well as rigid, the panel itself may be able to withstand an impact. However, if the panel does not give during an impact, the door may transmit the impact forces onto other hardware associated with the door. For example, the impact might damage door-mounting hardware, a door panel actuator or the seals. The damage could be very apparent, such as a completely inoperative door, or the damage could be difficult to detect, such as a seal that is only slightly bent or dislodged. If a damaged seal goes undetected, poor sealing could make it more difficult to maintain the proper temperature of the room, could possibly damage perishable goods stored in the room, or could cause a buildup of frost along the poorly sealed edges. Heavy frost accumulation on the seals can not only further diminish the effectiveness of the seal, but can also tear the seals as the door operates.
Although rigid door panels have their disadvantages, panels of insufficient rigidity can create problems as well. In many cases, an air pressure differential may exist across opposite faces of the door, which tends to push the door panels inward or outward. Even air pressure differentials created by a rapidly actuated panel cutting through the air can displace a relatively light panel out of its normal vertical plane. These situations can improperly position the door seals to create sealing problems similar to those caused by a damaged seal. But even if the seals are properly positioned, insufficiently rigid panels are unable to transmit the necessary compressive forces that are required to tightly set the seals. Thus, it can be difficult to provide a power-actuated, insulated door panel that is lightweight and has the proper balance of rigidity and impactability.
U.S. Pat. No. 5,080,950 discloses what appears to be a semi-rigid structural partition having some compressibility that allows it to be manually press-fit within a cargo compartment of a trailer. However, its structural properties are achieved by way of adhesively laminating several layers of materials (including multiple layers of foam material) to provide various degrees of flexibility, strength, and impactability.
In order to provide an insulated sliding door that is lightweight and resilient with the proper balance of rigidity and impactability, the door includes a door panel suspended from a carrier that travels along an overhead track. The door panel is able to transmit a significant compressive load (in a direction generally in the plane of the panel) while still being able to recover from an impact that temporarily deforms it. An actuation system moves the door, including such a panel, laterally relative to the doorway.
In some embodiments, a lightweight foam material provides the resilient core, and in other embodiments an inflatable bladder provides the resilient core.
Some embodiments include relatively rigid backup segments disposed around the perimeter of the door panel to facilitate the attachment of perimeter seals.
In some embodiments the rigid backup segments allow the door panel to flex between adjacent segments in response to a door impact.
In some embodiments, door seals are removably secured between rigid backup segments and cover plates to allow the seals to be readily replaced.
In some embodiments, a U-channel support beam connects a track-mounted panel carrier to an upper portion of a door panel, with the support beam being disposed under the panel""s outer covering to help prevent the door panel from pulling away from the beam.